Nylon-jacketed connector



Nov. 6, 1956 J, N, FREY 2,769,965

NYLON-JACKETED CONNECTOR Original Filed June 26, 1951 2,769,965 PatentedNov. 6, 1956 2,769,965 NYLON-Mercateo coNNECToR John Nelson Frey,Mountainsidc, N. I., assignor to The Thomas & Betts Co., Elizabeth, N.J., a corporation of New Jersey Continuation of application Serial No.233,662, June 26, 1951. This application March 7, 1956, Serial No.570,075

11 Claims. (Cl. 339-276) This application is a continuation of myco-pending application Serial No. 233,662, tiled June 26, 1951.

The invention relates in general to electric terminal tubular sleeves intelescopic coaxial relation, in which the outer sleeve constituted ashield of insulating material and the inner sleeve constituted a ductilewire-barrel adapted to be permanently deformed by the application of asqueeze pressure through the outer sleeve to crimp the inner sleeve intoa positive electric and mechanical connection with a wire or cabletherein.

More specifically, the invention relates to the wirebarrel portion of aterminal connector of the type which must he made very small, one marketrequirement of such connector being that the tubular assembly formingthe connector be about forty-hundredths of an inch in length andtwenty-four hundredths of an inch in outside diameter. It is mostimportant that the elements of the assembly be designed so that they canbe made cheaply and in large quantities as a factory product.

One diiiiculty which has been .experienced in the use of suchconnectors, particularly when made in such small sizes, is to preventflash-overs and tracking. An electric path is apt to form accidentally,leading from the high potential source in the cable conductors attachedto the connector, through, or more often around, the exposed ends of theouter insulating sleeve to ground on some object, and this possibilityof a Hash-over or tracking increases with increase of voltage, frequencyand lower air pressure at high altitudes.

Tracking as herein used and sometimes referred to as surface leakage orcreeping is the passage of current along a path over the surface of aninsulator.

4 One of the primary objects of this invention is to provide in suchconnector a longer leakage or tracking path than has heretofore beeneconomically possible, and thus increase the resistance to electricHash-overs without necessity of providing additional resistance materialparticularly for this purpose.

Broadly, this objective -is attained by providing one or msual outerinsulating sleeve and the current carrying elements of the connector,and located axially between the exposed ends of the conductors and theexposed ends of the insulating sleeve.

Certain commercial requirements of such devices are that they be capableof use in widely varying temperature conditions, for instance, in Arcticregions and in refrigerat ing apparatus where temperatures often reachminus 40 degrees F., and in fire control circuits and in varnish baking,where the temperature often reaches 400 degrees F. Another ieldrequirement is that these devices must be capable of withstanding theeifects of acids, alkalies and ketones, as well as salt water, aviationfuel, lubricating oils, carbon tetrachloride, hydraulic iluids and likedeleterious agencies with which they might come into contact. In so faras the outer insulating sleeve is concerned, it is required that it beof high tensile and compressive strength; capable of being molded to therequired cnfiguration; capable of being made translucent or colored; andhaving a long life under conditions which tend to destroy its insulatingproperties. The small all-over size of the connector herein featurednecessarily imposes a limitation on the cross section of material of thecoinposite members and this, in turn, complicates the problems indicatedby these commercial requirements and which the instant disclosure isdesigned to meet.

l0 It has been suggested in the prior art to form the innercable-engaging sleeve of the connector of a soft copper and to form theouter sleeve of rubber or of a thermoplastic material such asvinyldichloride or polybutene. When attempts have been made to form suchrubber, Vinyl- 15 chloride or polybutene insulating sleeves of thereduced cross section of material featured in this disclosure, thepremolded sleeves tended to and in time did collapse. For this reason,in the prior art devices the outer sleeve, irrespective of what materialit was formed, was intentionally made to adhere tenaciously to theconductorengaging copper sleeve and being thus internally reinforced theassembly maintained its intended configuration.

These prior art devices otherwise have not proven satisfactory in actualpractice for numerous reasons, including,

most seriously, a high production cost. In these known devices,especially where the outer insulating sleeve was thin, the action of thecrimping dies thereon had the effect i either of cracking open theinsulation or of at least thinning and sometimes actually tearing theinsulating material at its point of greatest deformation away from itsadherence to the underlying wire-gripping sleeve and thus presenting aspot or area of no insulation or of less than the minimum ratedinsulating effect required of such devices.

In the form of the invention herein specifically selected forillustration there is disclosed a form of electriciterminal connector,one end of which comprises an apertured tang or tongue formed integralwith a wire-barrel or inner sleeve of the improved connector forming thesubject-matter of this disclosure. The thickness of the apertured tongueextension of the inner wire-barrel and the size of wire to be securedtherein, as well as other factors not involved here, tend to prescribethe dimensions thereof, both internally and externally.

While it is of advantage to make the wire-barrel element of theconnector of soft copper, the electrical conductive requirementsnecessitate that it be made of somewhat thick cross section of material,and apparently this cannot be avoided despite the desire to make thedevice small.

There is also an advantage in internally reinforcing the outerinsulating sleeve and thus permit a reductionthereof in cross section,but it is not required that any such reinforcement possess anyconductive capacity and certainly t none comparable to the soft copperrequired 0f the wirebarrel element.

Accordingly, another object of the invention is to provide a multiplesleeve form of connector whose inner sleeve, while relatively thick asrequired, is deformable conventionally into crimped engagement with thebare wire or strands of the conductor intruded therein; whose outersleeve while thin is adequate in its insulating capacity and whichprovides for a crimping engagement with the insulation of the conductorby an intermediate sleeve 05 which does not necessarily have theconductive capacity members disposed in telescopic coaxial relation,featuring a thin-Walled, rigid, seamless metallic sleeve between theouter insulating sleeve and the inner wire-barrel or sleeve,`operativewto tie thecrimped Yinner` element -to `a portion of theconductor insulation; to give the maximum possible structural strength'and least addition of material for ithis-purpose'to lthe -partsWh-iehare to' be `radially deformed into al crimping .engagement lwithi theAwire: lor cable .inserted .in the l assembly.

Among the #other '-obiects of t'he invention r is' to Xprovide anelectric `terminalconnector of the type above outlined,

which will possess `thecharacteristics#commercially irequiredoflsu'chidevices Sas aboveindicatedandt at the same sleeve, lasmolde'dQibe vfequalto yor lnotf materially greater than the externaldiameter of the intermediate sleeve. As specifically required -by thisdisclosure, 'the internal diameter of the insulating sleeve as' moldedV`is preferably less than ftheiexternal diameter of the intermedi atesleeve.

This, in' Iturn, calls'I 'for Aa type of- Athermoplastic wmaterial fwhich can Abe molded to close tolerances, especially in forming -theboreof the insulating sleeve, and which has atleast a limitedplastic-memoryto shrink onto the intermediate 2lining andalimitedelastic recovery to form the airfgaps' herein-featured. -The choice of athermoplastic material capableof being so molded is restricted by othercommerciall requirements, lsuch as capacity to make it translucent, tocolor the same, to provide a narrow plastic range, i. e., 47-5degrees to5 l() degrees, and it'rnust possess other properties capable of beingeasily'c'ontrolledduring thel'molding cycle ofthesmall'size articlesherein'featured.

`Making `the outer-sleeve of a synthetic' condensation polymericamide'manuacturedunder the designationof nylon'j -and'oneform of-which`isdisc'l'osed in the patent to GoidonrNol' 2,348,536," granted'MayQ,1949, hasbeen l' most Ysatisfactory. VWhile this material `hereinafter-referredto generically-as nylonj is not as good an 'insulator as someother thermoplastics, thebetter insulating effects l of Ylsuch otherinsulating materialsA had 'to'be sacriing-advantages inherent in usingnylon.

"On -t-he'flotherhand, it has been foundin the instant situation-:thatwhenr4 acondensation polymeric-amide is used forthednsulating Vshieldits insulatingproperties are improvedduringuse; apparently dneito anorientation'of its crystals incidental 'to =the crimping` actionhereinfeaturd.

While it is the vintent to makethe'outer insulating sleeve of suchrigidity as will tend to resist collapsing and'thus maintain 'fitslconfiguration substantially as molded, the intermediate'liningsleeve,`of course, does act as an internal'reinforcement to the outersleeve toresist accidental deformation. The disclosure features for theintermediate sleeveL the use of a length of annealed commercial brassor-bronze, Ihereinafter referredto `generally as copper=`alloy, thebasic'stock of which can be purchased in the fopen market las tubing..Inone form of the inventionv where a'straight tube was used vitwas'simply cut oit from-aimarketsize of tubing and used 'as is withoutany machining. A cheaper methodis'to make the sleeve from flat strips ofthe alloy fed to an eyelet "machine, While brassfor lbronze'is not aparticularlygood electric conductoncompared Vwith copper,`Vthatiproperty is 2 not required' intheiinstant situation and, onthe-other h`and,

making thefsleeve'of brass' or bronze `rather'than' copper ficedsomewhat to obtain the vhigl-ily desirable compensati 50 contributesytothe desireto make the ysleeve very-thin, to give a high degree ofstrength to the metal part intended to be permanently deformed to resistsubsequent elongation, and to reduce as far as possible the presence ofa good conductor in the path of a possible flashback. While rigidity isindicated, it is understood vthatlthe-sleeve must not be so rigid in itscross section as would offer any materal resistance toradial'deformation or` otherwise defeat theindicated crimpingoperatiomnor so rgidas to resist the desired interlocking incidental tothe `'crimping operation of the two inner sleevesof `theconneetor-herein featured.

The inner wire-barrel or sleeve is formed of veryvsoft sheet copperwhich can be rolled into the cylindrical form herein featured and whichhas a conically flared end which can be easily distended radially, asherein indicated, into the required binding. engagement with 'the rigidintermediate sleeve and to form the funnel-shaped entranceat thefree endthereof, as hereinafter described.

Theinvention also relates to an improved technique in forming anassembly of such a connector withthe wire or' cable' therein topi-Ovidethe finished assembly.

Various'other objectsand advantagesof'rthe invention willbe in" partobvious frornan inspection of the accomp'anyingdrawingsand in part will.be more fully forth in the following particular description of one formof connectorv embodying the inventionand of one method of attaching theconnector to a cable, and theinventionalso consistsin certain new andnovel .features of construction and combination Vof parts hereinafterset forthand claimed.

" In'the accompanying drawings,

Fig.' l' is an enlarged view partly in section showing a preferredembodiment ofthe 'invention deformed into a permanent crimpingengagement with an Velectric cable intrudedinto' its wire-barrel endand'ill'ustrating the assembly of' connector and cable in'ithefin'afform it assume- 1sv following a 'time' delay' after crimping;

Figsj'2 through 5 are each transverse sectional views throughtheassembly shown in Fig. l, 3 being taken ontheline 3--3, `to showsubstantial recession offthe outer insulating sleeve from theintermediatemet'al sleeve, upon completion of a crimping operation `asin Eig.' 2;

Fig. 4 is taken onthe line' t4-4i of Fig. l, showing anv intermediatestage of thecrimped outer insulating sleeve engagingthel intermediatemetal sleeve substantially about its entire periphery;

Fig. 5 is taken on the line S-" of Fig.' l, -showing'the outerinsulating sleeve as spaced from the crimped free end' 'oftheintermediate metal sleeve to'form insulating air gaps therebetween asindicated atV 42 and'43 in Eig l;

Fig.l 6 is a View in end elevation `ofthe connector per seg, consideredasv Fig. 7 is a plan viewl of the connector, an articleror manufacture,in its marketed form before being crimped tonto the cable and showing anaxial section taken on the line 7-7 of Fig. 6; and

Fig. Sisa viewin axial section of the component elementsoftheconnectorlshown in Figs.A 6Aand 7 assembled in position' in' thematrixA of a die-punch machine and'showing a mandrel punch in positionabout to upset anend of the Vinner sleevelinto engagement with theshoulder ofthe intermediate sleeve to effect a permanent connectiontherebetween.

In the several viewsoflthe drawingsand 'r'efering'rst to' the. showingof 'the' stock device in Fig. 7, thereis disclosed 'anV electricterminal connector 1t) provided at one 'end with 'an apertured tang'ortongue 'llinand the other end'of which comprisesa"cylindrical'portioni'Z formed of three' tubulanmembers in coaxialtelescopic relation, particularry' constituting the subject-matter 'ofthisdisclosu're. l The tongueincludes a narrow neckjportion 13 whichforms an integral extension'from'the'inne ofthe "three'tubular membersformingv the 'connector 'as liereinafter1 described.

The outer memberl 14 oflthe improvedconnectorlis a one-piece, preformed,relatively thin, molded "sleeve `of lthe intermediate rigid liningformed of nylon, and thus, as above noted, having at least someinsulating properties. The end portions and 16 of the `sleeve 14 areeach of cylindrical form and are of diiferent diameters, with aninclined annular shoulder 17 mid-length of the sleeve 14, integrallyconnecting the end portions and facing the end portion 16 of largerdiameter. The nylon sleeve 14 is dimensioned in its process `of beingmolded so that, when stretched slightly as hereinafter described, theends of its bore will have diameters exactly equal, respectively, to theoutside diameters of an intermediate, rigid lining sleeve 18 of theassembly, and the shoulder 17 will conform more or less exactly to a twith a corresponding shoulder 19 on the in Fig. 1, the smaller providedwith an inwardly-projecting annular ange 24) molded integral therewithand forming a stop for the intermediate and inner sleeves of theconnector in those cases where such a stop flange is prescribed.

The nylon sleeve 14 is initially molded to have an internal diameterslightly less than the external diameter sleeve 18, and originally thesleeve 14 has the unorientated and substantially unstressedcharacteristics of molded nylon. The part of the nylon sleeve 14 whichtelescopes the lining sleeve 18 is stretched slightly as it is locatedin place. This has the effect of initially working the stretched partradially at least to a limited extent so that, when so stretched, itevidences a greater mechanical strength and a greater resistance to anelectric break-down than would be the case if it were not so stretched.At this point the nylon sleeve evidences some plastic memory and in itstendency to shrink to its molded form it adheres to the intermediate`sleeve and in its frictional engagement therewith tends to resistaccidental separation therefrom in an axial direction.

The intermediate sleeve 18 has a length in its end 21 of reduceddiameter, extending for the length of the corresponding end portion 1Sof the outer sleeve, and in its end 22 of larger diameter terminates inspaced relation to the wide-open end of the large diametered portion 16of the louter sleeve to form an overlap area 23 preferably of sufficientaxial length to eliminate, or, at least, tend to eliminate possibilityof flash-backs between the inserted cable and articles exterior of andadjacent tothe connector. The inner surface of the nylon sleeve 14 andthe outer surface of the copper-alloy sleeve 18 are made smooth at theirareas of contact forming the joint 24 therebetween so as to offer, in sofar as the surfaces are concerned, minimum resistance to any relativecreeping of these members during the subsequent crimping step.

The inner sleeve 25 of the connector is integral with the neck 13 andtongue 11 and is formed as shown in Fig. 6 by bending winged extensionsthereof about a mandrel into a closed tube or sleeve 26 with its freeedges meeting to form a closed joint 27.

' As shown in Fig. 7, the inner sleeve 25 is a straight cylinder and hasinitially a press t in the end 21 of reduced diameter of theintermediate sleeve. The purpose of this press fitting of the parts isto prevent opening of the joint 27 when the connector is crimped ontothe cable as hereinafter described. The presence of any such open jointwould form a crack into which strands of the wire conductors mightextend, with resulting impairment of the desired good mechanical andelectric contacts. Maintaining the joint closed defeats any suchpossibility. Initially, the extension 29 does not contact theintermediate sleeve 18 and its conical throat has an angle less than itspunch angle as finally formed and shown in Fig. 7. As initiallyassembled the prestretched nylon sleeve 14 is fast on the intermediatemetal sleeve 18 and the sleeve 18 pressatitted on the inner wire-barrelor sleeve `The connector as an article of manufacture is formed in athree-step operation, which steps may take place simultaneously in adie-press operation. First, the,in

termediate copper-alloy sleeve 18 is gently forced against anyincidental frictional resistance, with its smaller end in advance, intothe momentarily stretched outer nylon sleeve 14 and until the shoulders17 and 19 abut as shown in Fig. 8. The stretched insulating sleeve isthen permitted to contract into a resilient engagement with the sleeve18. At this time the insulating sleeve and intermediate sleeve areretained in their positions as so set by reason of the tendency of thenylon sleeve to recover its molded configuration with resultingfrictional engagement between it and the sleeve 18, and this is sucientto resist any accidental relative separation.

The assembly of the insulating sleeve and intermediate sleeve isinserted in the cavity or matrix a of a diepunch machine fashioned toreceive the same as shown in Fig. 8. The inner sleeve 25 is locatedsnugly within the bore of the sleeve 18 approximately in the position itwill assume in the completed structure, with its internally tapered freeend spaced slightly from the shoulder 19 and its opposite end positionedagainst or almost against a stop wall b forming the bottom of thecavity.

The die-punch machine includes an upsetting punch or mandrel c movablewith its line of thrust coinciding with the axis a*b of the connector.The advance end of the punch is provided with a long cylindrical head dwhose diameter is either exactly that of the diameter of the bore 28 ofthe inner sleeve or of a very slight increase in diameter to force-titthe inner sleeve 25 against the intermediate sleeve, care beingexercised not to open the joint 27. The head d is thus `designed ofsufficiently small diameter so as to avoid any material expansion ofeither the inner or intermediate sleeve, as the intent here is to leavethese tubular members substantially as originally dimensioned and intheir press-t relation. The punch is provided at the inner end of itscylindrical head with a shoulderaforrning enlargement e for upsettingthe end 29' of the sleeve 25 to form ange 29 in permanent contact withand conforming in contour with the shoulder 19,. and thus form thewide-open funnel-forming throat 31 shown in Figs. l and 7. In theinstant case shoulders 17 and 19 extend at an angle of about 45 degreeswith the axis a-b, and the enlargement e likewise extends at an angle of45 degrees. This means that the extension 29', Fig. 8, has been spreadopen by the axial advance of the punch from its initial 30 degreesinternal Hare into a 45 degree angle with some incidental thinning ofthe throatforming flange 29 at its outer perimeter as shown in Fig. 7.

In use the cable C is first prepared by stripping back its insulation Ito expose an end of the conductor wires W forming its core. is insertedinto the large intake end of the connector until the insulation I abutsagainst the inclined flange 29' and which forms a stop for limiting theinsertion thereof. By the use of suitable crimping tools a squeezepressure is applied to the diametrically opposite sides of the outervnylon sleeve rst in the region of its smaller diameter, Aalong thepressure lines indicated by the long arrows in Fig. l and thus along thesection line 3-3, to transmit the pressure through the three tubularmembers, deforming the outer nylon sleeve 14 into an interlockingengagement with the intermediate sleeve 18, deforming the intermediatesleeve into an interlocking engagement with the inner sleeve 2S, anddeforming the inner sleeve into a permanent crimping engagement with theexposed Wires, somewhat following conventional practice in this respect.rEhen a relatively light squeeze pressure is applied in the planerepresented by the short arrows at the right of Fig. 1, thus along thesection line 5-5, to transmit pressure through the two tubular members,deforming the outer nylon sleeve into an interlocking engagement withthe intermediate sleeve 18 and deforming it into permanent engagementwith the cable insulation I. At this time, the right end portion of thenylon sleeve 14 is free to creep towards the right without resistancefrom the in-4 termediate sleeve 18, which is also free to distendslightly` to the right as may be necessary. j i

The stripped-back end of the cable 'Of course, the cross sectionalconfiguration ofithe 'assembly offFig. 1 in the areas crimped willatleast Vinitially take the form imposed vthereonby the work faces ofthe crimpingdies or tools. -In the case vherein illustrated theconnector is squeezed'between,power-operated dies. The dies whichoperate along 'the 'line 3 3 have at faces, while those which operatealong theline '5-5 have faces with opposing dat arcs and whose faces onopposite sides of the arcs are slightly spaced apart when the dies arein theirpositionof nearest approach.

Considering the init'ally dead soft, copper inner sleeve 25, thedisclosure features the use of sufficient cross section of material suchas may be necessary to carry the Voltage for which the device isdesigned, and this, in turn, calls `for the relatively thick-walledwire-barrel or sleeve 2'5 Vherein disclosed. While there is some slightaxial elongation of the inner sleeve 25, incidental to the crimpingoperation, any such axial elongation vis dimensionally about the same asthat of the intermediate sleeve 18, so that there is no noticeableVseparation of thecopper and copper-alloy members. The inner sleeve 25is not only deformed radially and slightly in an axial direction, butthemetal'is coined as the result of the crimping, so that in its viinalform the part `forming the inner sleeve 25 of the connector is harderand stronger as it reaches its final contour than when initially rolledinto its cylindrical form as shownl in Fig. 6.

'It will thus be seen that in the `final connector-cable assembly vasshown in Fig. 1 the relatively tough but thinwalled intermediate sleeve18 is permanently secured at one end to the inner, dead soft copperwire-barrel or sleeve 25 by reason of being crimped thereto in the actof crimping the member onto the exposed ends yof the wires forming thecore of the cable. The free end of the sleeve 13 in the portionprojecting beyond the wirebarrel or sleeve 25 is permanently secured tothe insulated part of the cable, so that the insulation I is tied by thesleeve 1S immovably to the inner sleeve 25 and thus to the bared 4endsof the wires W. In this way any pullapart load on the tongue v11 andcable C will be resisted by both of the crimpings in the planes 3-3 and5-5 and by the non-distensible intermediate sleeve 18.

Reverting to aconsideration of what takes place during the firstsqueezing operation, it is noted that the application of pressure on thenylon sleeve tends to elongate both the outer and intermediate sleevesin-both axial directions from the ,plane of the applied pressureindicated by the lQrlg arrow. The .elongation of .the nylon sleeve 14will be slightly-greater than the elongation ofthe intermediate sleeve18. As the 'adhesion between the nylo-n sleeve and the` intermediatesleeve is simply that of the initial frictional snug t,.and asthe'crimping force must be sufficient to deform the innermost relativelythick coppersleeve 2S, Stuchforce is .sufficient to overcome anyfrictional resistance .to :relative elongation, 'and the nylon sleeve isfree t o readjust ,itself .by creeping valong the surface of theintermediate sleeve 13 without lany noticeable resistance tothedeformation of either of the sleeves. Nylon is capable of beingstretched up to five hundred per cent of its'original length. In thisway there is avoided any tearing action `of the nylon insulating sleeve,such as would occur-if the insulation were-bonded to the metal sleeve18. As ythe kintent here is to provide sufficient cross section ofmaterial in the insulating sleeve 14 under all service conditions tolgive it the requisite insulating shielding, it is tothe vnoted rthat inmolding the sleeve vit be made sufficently :over-size as to itscxtern'aldiameter to compensate for any such thinning as -may result from theelongation imposed Ythereon lby the crimping step.

`As the `result of subjecting the initially cylindrical form F of1nylonsleeve tothe squeezing effect of the crimping tools, :the sleeve 14, inthe region of the plane indicated bythe section 3-'3, changes from acylinder into an allover-elliptical form `in cross section, as shown inFig. 2. At the same time the cross-section-ofmaterialat the point ofgreatestsqueeze, tends lto Ithin out so that there is "a sectionofleastthickness at32. Apparently,'thereis'some cold flow of theplastic, so thatthe roundedends 33, y34 are of lgreatersectionofmaterial than when'intheiriinitial molded Vandislightlydistended form.

The inner and intermediate sleeves 2S'andl8take thelconstricted-'waistform-with the strands ofthe conductor compressed and`incidentally deformed from 'their 'wire configuration as retainedexteriorly of'thecrimpedareas.

Theintermediate sleeve 18 is not materially changed'in its cross sectionof material, more or lessmaintainingits initial thickness, Vbut the softcopper 'inner sleeve 25 lof -the connector tends to'thin out slightly inthe-portion 35'subjected'to the greatest pressure as maybe observedin`Figs. 2 Vand 3, and `there-is some cold ow'of'the copper therefrominto the rounded ends 36. As the result of this action both theintermediate and inner vsleeves become worked and thus coined, withanincrease in strength in the portions so crimped. Of course, thethinned out midportions 32 of the nylon sleeve 14 when squeezed'bythecrimpingtool follow the intermediate sleeve18, or, rather, advanceinwardly with it and momentarily adhere tothe same,'as shown in Fig. 2.Thereafter, the deformed nylon sleeve graduallyand slowly recedesoutwardly away from the intermediate sleeve 18. The outward recession ofthe nylon sleeve 'becomes greatestat its point of greatest inwarddeformation, so that the space 37 forms gaps of greatest width in the.line of the squeeze load, and these gaps, top and bottom, as shown inFig. 3, gradually reduce in width ktowards points 3S, 'four being shownin Fig. 3. The rounded ends 33, 34 of the nylonsleeve "14 move outwardlyslightly along the major axis of the ellipse away from the rounded endsvof the intermediate sleeve 1S to 'form relatively thin secondary endgaps'39. rThe gaps 37 and 39 are in intercommunication and coact tovform in elect a single .clearance and thus 'anair 'insulating space.between the outer nylon sleeve 14 and the intermediate crimped sleeve18.

A similar void is established in the region of the squeeze load imposedon the .cable insulation JI in the plane 5-5, Fig. l. As this portion ofthe connector is squeezed between the faces of crimping dies or tools,the squeeze pressure acts .through the nylon sleeve Vand through thesleeve 18 to compress the cable insulation at least slightly. At .thesame time the sleeve 18 .becomes deformed from its initial cylinder intoa formresembling in its midportion a fiat ellipse provided atdiametrically opposite sides with side portions bent back uponthemselves to form side ribs 40, 41. At this time the nylon sleeve 14conforms somewhat to the winged contour of the sleeve '18, at least aslong as the assembly is under load from crimping apparatus and, ingeneral, the parts take the form shown in Fig. 4. Thereafter the nylonsleeve, in to its initial molded shape, -distends `outwardlyandseparates from the intermediate sleeve 18, and thus forms an upper,internal, air-insulating clearance 42 and a-similar lower, internal,lair-insulating clearance 43, as best shown in Fig. 5. Apparently thereis not always a complete recovery of the nylon sleeve 14 .either back`to its cylindrical form as molded nor even into its elliptical formresulting from the crimping operation for remnants of the dieimpressions are often still present after along period of time as fourshallo-w indentations 44, shown greatly enlarged.

Considering the finished device as shown in Fig. 1.

it is seen that in order for a dash-over or a tracking ofelectriccurrent tooccur it would have to traversea path from the energized wiresW through the inner wire-engaging sleeve 25 and intermediate sleeve 18to the y'exterior 4of the insulating sleeve 14, lapping about the .opencable-receiving end thereof. mediate sleeve 1S yis not intended to be aparticularly good conductor, it i-s possible that the overlap area 23covered :as 'it more or less is A-by' the insulation lI,-

its inherent tendency to revert more or lessl Realizing that the inter-w-placed on the gap 23 to avoid will tene torpr'eve'nt flash-backs at theopen end of the connector. However, the intermediate `sleeve 18 doesconstitute a conductor and dependence cannot always be dash-backs fromthe open end of the insulating sleeve 14 to the adjacent edge of thesleeve 18, especially in the presence of currents of high voltage.Tracking which may occur in the presence of currents of low voltage ismore likely to develop and, also, possibility of tracking is more likelyto occur after the connector has been in use for a long time and whereenvironmental climatic conditions tend to provide an electric path aboutthe insulating sleeve 14 both exteriorly and interiorly. One suchpossible path is shown by the dots 45 in Fig. l leading from the outerperimeter of the insulating sleeve 14, about its edge encircling thecable insulation I, and then along the inner wall to the point where thesleeve 18 bends inwardly away from the insulating sleeve 14 at about theplane 4-4.

In effect, the presence of the air spaces 42 and 43 lengthens `theoverlap 23 by the distance between the end edge of the sleeve 18 and theplane 4-4 and in this way any leakage path is elongated.

While the air spaces 37 and 39 are not in the path of any electrictracking, it is noted from the showing in Fig. 3 that these spacespractically encircle the intermediate sleeve, supplement the insulatingeifect provided by the outer insulating sleeve; and thus contribute tothe provision of a thin insulating sleeve while avoiding electriccurrent penetration therethrough.

These air gaps are eachof some material length meas ured in thedirection of any such electric flash-over or tracking and being eitheriilled with air, or more possibly, in the case of the spaces 37, formingvacuum spaces, function as electric insulators, defeating anypossibility of Hash-overs or tracking even in the absence of the flange20.

While the invention has been illustrated and described with respect to apreferred embodiment thereof, it is to be expressly understood thatvarious changes and modifications may be made therein without departingfrom the inventive concept underlying the same. Therefore, the inventionis not to be limited except insofar as is necessitated by the prior artand the scope of the appended claims.

I claim:

1. In the art` of crimping an electric connector onto a conductortherein, wherein the connector comprises three preformed members intelescopic relation, the inner member being a sleeve of highlyconductive malleable metal fashioned toform mechanical and electricalengagement with a conductor therein, the intermediate member being asleeve of thin malleable metal and the outer member being a sleeveformed of insulating material having plastic memory and capable ofautomatically distending outwardly towards its original configurationwhen free of inwardly deforming forces, and wherein the outer `Sleeveinitially has an internal diameter slightly of the intermediate sleeve,in momentarily stretching the gouter sleeve, drawing the outer sleevewhile so stretched over the intermediate sleeve to cause theouter sleeveto engage the intermediate sleeve friction'ally but otherwise free tocreep thereon, subjecting the connector s'o assembled for a limitedlength area so squeezed to recede outwardly by virtue of its plasticmemory from the inwardly deformed portion of theintermediate sleeve,thereby to f'or'm an air spac between the outer and intermediate sleevesat the place so deformed while permitting readjustments to take placeautomatically between the outer and intermediate sleeves.

2. In the art of crimping an electric connector onto a conductortherein, wherein the connector comprises three performed members intelescopic relation,I the inner member being a sleeve of highlyconductive malleable metal fashioned to form mechanical and electricalengagement with a conductor therein, the intermediate member being asleeve of thin malleable metal and the outer member being a sleeveformed of insulating material having plastic memory and capable ofautomatically distending outwardly toward its original configurationwhen free of inwardly deforming forces, and wherein the outer sleeveadheres to said intermediate sleeve frictionally and is otherwise freeto creep thereon, the method which consists in subjecting the connectorfor a limited length thereof to a crimping squeeze force applied fromthe outside through all three sleeves, with a force suilicient to bendinwardly both the inner and intermediate sleeves beyond their respectiveelastic limits and thus permanently de form the inner sleeve into acrimped engagement with conductors therein and thus to deform both theinner and intermediate sleeves into an interlocking relation, subjectingthe outer sleeve and the intermediate sleeve at oney end thereof to acrimping squeeze force applied through the outer sleeve with a forcesulicient to bend inwardlyl the end of the intermediate sleeve beyondits elastic limits, and releasing the connector from all deformingforces acting thereon to permit the outer sleeve in the areas sosqueezed to recede outwardly by virtue of its plasticl memory from theinwardly deformed portions of the intermediate sleeve, thereby to forman air space between the outer and intermediate sleeves atthe two placesso deformed,

3. An electric connector including three tubular mem bers in telescopicrelation and comprising an inner sleevefrictional engageotherwise freeto leable metal and of less electric conductive capacity than the innersleeve, said inner and intermediate sleeves being mutually deformedinwardly each beyond its elastic limit to connect the same permanentlyinto a crimped relation, and the outer member constituting a premoldedsleeve formed of a plastic insulating material capable of transmittingsqueeze forces therethrough without rupturing to effect such mutualdeformation of the inner and intermediate sleeves, said outer sleevehaving plastic memory and capable of distending outwardly towards itsmolded form when free of such squeeze forces, and said intermediate andouter sleeves spaced apart at the portion sov crimped to form an airspace therebetween by reason of the outer sleeve receding outwardly fromthe intermediate: sleeve by reason of its plastic memory and the side ofthe outer sleeve forming said air space forming a tracking' path.

5. In a device of the class described, an insulated cable having `a bareend of its vconductor projecting beyond its 11 insulation, alterminalconnector formed of three telescoping tubular members with the conductorbare ends locatedwithin the innermost member, an intermediate sleeve ofmalleable metal having one end portion thereof proiect-ing beyond theinnermost member, telescoping the insulation of the cable and havingsaid end portion permanently bent inwardlyon the cable insulation, andthe outer member beingA premolded approximately to shape and formed of aplastic insulating material having plastic memory and capable ofdistending outwardly towards its molded formy when free ofinwardly-directed deforming forces, with the inwardly bent end of theintermediate sleeve andthe outer plastic member spaced apart to form anairspace therebetween with the part of the plastic member'facingsaid-space forming a tracking path.

6. VIna device of the classl described, the combination of an outersleeve of insulating material, a metal tube within the bore of the outersleeve and in part lining the same, one end of the metal tube beingspaced axially inwardly from'thel adjacent end of said outer sleeve toform the outer sleeve with an overlap area providing initially arelatively short tracking path on the inner surface of the outer sleeve,the end of the inner tube at said overlap area being bentv inwardly awayfrom the outer sleeve to formv a space therebetween to lincreaseinwardly the length of said short tracking path.

7. In a device of the character described, an insulated cable having abare end portion of its conductor extending beyond its insulation, aterminal connector formed of three telescoping tubular members as a unitwith the bare end portion of said conductor intruded within theinnermost member of highly conductive metal, an intermediate member ofrelatively thin malleable metal having one end portion thereof extendingbeyond the adjacent free end Vof said innermost member and telescopingthe insulation of said cable, said innermost member comprising a tongueand a barrel portion coextensive therewithfwith its said adjacent freeend upset within said intermediate member to secure said members againstrelative movement, and a premolded outer member of liexible insulatingmaterial having lastic memory and capable of receding substantiallytoward its molded form when free of inwardly-directed deforming forces,said innermost member being crimped on the intruded portion of saidconductor through said outer member and said extended end portion ofsaid intermediate member being bent inwardly on said cable insulationthrough said outer member at diametrically opposite points thereonwhereby the said extended end portion of Vsaid intermediate member isspaced in part frornportions of the inner periphery of said outer memberto lengthen a tracking path thereon'.

8. In an electric terminal connector comprising a plurality ofVtelescopically arranged members, the combination of an inner sleeve or"highly conductive metal including an'integral tongue portion, anintermediate sleeve of thin ductile metal having a common wall thicknessthroughout and opposite end portions of differing diameters forming ashoulder therebetween, said inner sleeve havinga press-tit in one endportion of' said intermediate sleeve with its intruded'free end upsetagainst the inner face of said shoulder to securesaid sleeves againstrelativeV movement, and an outer sleeve of molded insulating materialhaving a force f1t on said intermediate sleeve with one end portionthereof extending beyond the free end of said intermediate sleeve, saidinner sleeve being adapted to be crimped on a bare end portion of aninsulated conductor and the free end portion of said intermediate sleevedeformed inwardly on the insulating sheath' of said conductor throughsaid outer sleeve, said outersleeve having plastic memory and capable ofreceding substantially to its original form when released frominwardly-directed deforming forces whereby portions of said outer sleeveare spaced from deformed portions of saidintermediate sleeve to providean air space therebetween, the majorV portion of said outer sleeveremaining l2 at all times in tenacious frictional engagement with said'vintermediate sleeve but free to yield thereon in response toinwardly-directed deforming forces.

9. in an electric terminal connector comprising a plu-- rality oftelescopically arranged members, the combina tion of an inner sleeve ofh1ghly conductive metal including an integral tongue portion coextensivetherewith, an intermediate sleeve of thin ductile metal having aA commonwall thickness throughout and opposite end portions of diiferingdiameters forming an inclined shoulder therebetween, said inner sleevehaving a press-tit in the reduced end portion of said intermediatesleeve with its intruded end upset on said shoulder therein to securesaid sleeves against relative movement, and an outer sleeve of moldedinsulating material having a force t onV said intermediate sleeve withone end thereof extending beyond the free end of said intermediatesleeve, said inner sleeve being adapted to be crimped on the bare endportion of an insulated conductor through said outer sleeve, and thefree end portion of said intermediate sleeve deformed inwardly on theinsulating sheath of said said intermediate sleeve to provide an airspace therebetween, the balance of said outer sleeve remaining at alltimes in tenacious frictional engagement with said intermediate sleevebut free to yield thereon in response to a crimping operation. Y

10. In an electric terminal connector comprising a plurality oftelescopically arranged members, the combina- -tion of an inner sleeveof highly conductive metal, including a tongue portion coextensivetherewith, said inner' sleeve having its free end internally-tapered toreduce the wall thickness thereof, an intermediate sleeve of thinductile metal having a common wall thickness throughout and opposite endportions of different external and internal diameter defining aninclined annular shoulder' therebetween, said inner sleeve having apress-lit in the smallest end portion of said intermediate sleeve withits tapered free end upset on the inclined shoulder within saidintermediate sleeve, and an outer sleeve of molded insulating materialhaving a tenacious frictional t on said intermediate sleeve with one endthereof extending beyond the free end of said intermediate sleeve, saidinner sleeve being adapted to be crimped through said intermediate andouter sleeves on the bare end portion of an insulated conductor whenintruded therein and the free end portion of said intermediate sleevedeformed inwardly through said outer sleeve into permanent crimpedrelation with the insulating sheath on said conductor, said outer sleevehaving plastic memory and capable of substantially receding toward itsnormal coniiguration when released from inwardly directed deformingforces whereby deformed areas of the outer sleeve are-spaced from thedeformed portions of said intermediyate sleeve to provide an air spacetherebetween, the balance ofthe outer sleeve remaining at all times infrictional engagement with said intermediate sleeve and free to yieldthereon in response to a crimpingoperation.

l-l. In an electric terminal connector comprising a plurality oftelescopically arranged members,rthe combination of an inner sleeve ofhighly conductive metal including a tongue portion coextensivetherewith, said inner sleeve having its free end internally tapered toreducethe wall thickness thereof, an intermediate sleeve of thin ductilemetal having a common wall thickness throughout andopposite end portionsof different external and internal diameter dening an inclined annularshoulder therebetweem said. inner sleeve having a press-fit in thel saidintermediate sleeve, an outer sleeve of molded insulating materialhaving plastic memory in tenacious frictional engagement with saidintermediate sleeve, one end of said outer sleeve extending beyond thefree end of said intermediate sleeve, and an insulated cable having abare end cportion of its conductor intruded into said inner sleeve fromthe extended free end of said outer sleeve with the adjacent end of theinsulating sheath of said cable intruded in the free end of saidintermediate sleeve substantially in abutment with the upset end of saidinner sleeve, said inner sleeve being crimped on said intruded conductorpor-tion through said outer and in- 10 ing a longer tracking path.

No references cited.

